Worksheet

Part One - Background information

Copy the information below into your background section on your worksheet.Today you will observe another protist. In the previous lab (online or in class) you observed a type or protist called a protozoan. Recall that protozoans are animal-like protists. That is, they have similar characteristics to animals. Mainly, they are heterotrophs and they must hunt for their food.

Recall that protozoans can be classified by how they move. In the last lab you observed a type of sarcodine called an amoeba. All sarcodines move by using pseudopods, or temporary bulges in the cell membrane.

The protozoa you will observe today is called the paramecium. A paramecium is unicellular and moves by using cilia. Cilia are short, hair-like structures that are found on the surface of the organism. Cilia have three uses: 1.movement, 2.capturing food, 3. sensing the environment. When you observe the paramecium it may look like it only has cilia on part of its cell. In fact, the entire cell is covered in cilia! Think of it like a furry stuff animal. All of it is covered in hair. Similarly, all of the paramecium is covered in cilia, not just the "edge" of it. Observe the video below to see the cilia move on the paramecium.

Part Two - Cell Structures

Labeled diagram of paramecium.

Identifying structures in the paramecium is rather simple! As you read the information, fill in the blanks on your worksheet and identify the structures on your diagram.

First, observe the outside of the organism. What appears to be the cell membrane is actually a part called the pellicle. The pellicle is a stiff, outer covering that helps give the paramecium its shape. Unlike the amoeba, the paramecium is not able to change shapes (although it can bend and twist). Just below the pellicle you will find the cell membrane.

On the surface of the organism are short hair-like structures are the cilia. As you already learned, the cilia have three functions: to help the paramecium move, to help it capture food, and to help it sense the environment. Also on the surface you will find an indentation called the oral groove. The oral grove is lined with cilia to help the organism capture food. At the end of the oral grove is where the paramecium takes in its food through endocytosis. The food enters the organism and becomes trapped in a food vacuole. The vacuole stores the food and is broken down when it combines with a lysosome. You may also be able to observe a part on the surface called the anal pore. The anal pore is where the waste leaves the organism.

Inside the organism you will also note a star-shaped organelle. This is the contractile vacuole. As with the amoeba, the contractile vacuole collects and removes excess water. You can observe the contractile vacuole work in the video. Also inside you will find not one but TWO nuclei. The large nucleus controls the day-to-day functions of the cell. The large nucleus is visible and is a slightly different color from the rest of the organelles. The small nucleus only controls reproduction.

Paramecium can reproduce in two ways: asexually through binary fission and sexually through conjugation. In our bacteria unit we learned what binary fission and conjugation are. The same processes are true for paramecium. In binary fission, the cell splits in two and each cell receives the same copy of DNA from the parent cell. In conjugation, the paramecium shares genetic material with another paramecium before splitting. After splitting, each paramecia now has different DNA than the parent originally had.

Labeled diagram source: http://bilingualbiology10.blogspot.com/2010_10_01_archive.html, modified to match the vocabulary of this online lab.